1. Field of the Invention
The invention relates to a method for operating an electric window lift for closing a side window of a vehicle, for example, a convertible vehicle. The invention further relates to a device for carrying out the method of operation.
2. Description of the Background Art
An electric window lift is used for automatically opening and closing a side window of a vehicle. Closing the window causes it to move in a known manner from a lower initial position, in which the window is open, to an upper final position, in which the window is closed. The path that the window travels in this process can be hereinafter referred to as the actuation path. The instantaneous position of the window along its actuation path can be referred to as the actuation position.
Electric window lifts are generally equipped with what is called anti-pinch protection, i.e., with a function of the window lift control by means of which the window is reversed, or at least stopped, when it encounters an obstacle during the closing process. Such anti-pinch protection serves to ensure that no object, and especially no body part, is pinched between a top edge of the window and a window frame—or a vehicle roof in the case of frameless windows—during automatic closing of the window.
The speed of an associated window lift motor is often monitored to detect a pinch event. The speed or another operating quantity derived therefrom is continuously compared with a stored threshold value. In this scheme, a pinch event is inferred when the speed drops below the threshold value or when the threshold value corresponding to the other operating quantity is exceeded in a positive or negative direction—depending on the definition of the operating quantity.
However, variations in the speed arise not only in a pinch event, but also in normal operation of a window lift, predominantly influenced by the varying running resistance of the window over the actuation path. In particular, a significant drop in the speed regularly occurs in this process at the upper end of the actuation path, when the upper edge of the window enters the top window seal shortly before the final position is reached. In order to reliably avoid false triggering upon such a “system-related” drop in speed, i.e. an erroneous detection of a pinch event that is not actually present, frequently the threshold value is not specified as a constant, but instead as a function of the actuation position.
However, since the system-related fluctuation in the speed also varies with time, for example as a result of the changing outside temperature or aging of the window seal, the actuation-position-dependent function of the threshold value often is not rigidly predefined. Rather, in this case the actuation-position-dependent threshold value is continuously adjusted by the window lift controller. This adjustment is typically referred to as adaptation. Here, the window lift controller “learns” where a recurring sluggishness is present and raises or lowers the threshold value in this region of the actuation path accordingly.
Such adaptation is problematic with convertibles, since the top window seal is only present when the top is closed and not when it is open. A threshold adaptation that had taken place with the top closed would thus disadvantageously be “unlearned” again when the top is open. This can have the result that the entry of the window into the roof seal once the top is closed again is erroneously detected as a pinch event, and the window is accordingly “mis-reversed.”
In conventional window lifts for convertibles, this problem is often solved by the means that the adaptation is completely switched off when the top is open. Disadvantageously, this can have the result that ongoing relearning of the adaptation occasionally does not take place over long periods of time. This can lead to a variety of malfunctions of the window lift, especially when the top is closed after the vehicle has been parked for long periods with the top open.